Skip to main content

Full text of "Measurement of Regional Gobbling Phenology in Missouri"

Measurement of regional gobbling phenology in Missouri 

Summary of the 2007 spring data collection period 
Jeff Beringer, August 2007 

Introduction: 



A conservative season timing and harvest structure is an important component of MDC's 
successful turkey management program. Missouri's turkey season is timed to coincide 
with the onset of continuous incubation by hens, usually starting around the 3 week in 
April. Opening the spring season at this time ensures that all hens have been bred and 
many are on nests and protected from harvest. The 3 week opener likely reduces 
overharvest of male turkeys but may result in reduced gobbling activity. Gobblers can be 
very vulnerable in early April, and a later season ensures that we don't overharvest this 
segment of the population. 

Gobbling activity is considered by hunters to be an import component of spring turkey 
hunting. MDC has set the opening date of spring season to coincide with the "2 nd peak" 
of gobbling. This "2 nd peak" is generally thought to occur around the onset of continuous 
incubation by hens and has been supported by research projects in South and North 
Missouri, however studies in Mississippi and Iowa did not find a 2 nd peak of gobbling or 
a distinct relationship with nesting activity. Recent hunter input from informational 
meetings, email, letters, post season surveys and phone conversations suggest that many 
hunters believe that Missouri's turkey season occurs too late in the spring. Hunters often 
use the phrase "the birds are gobbled out before the season even starts." We are 
conducting this gobbling phenology study to measure the timing and extent of gobbling 
activity throughout Missouri. Besides biological insights the study offers a great 
opportunity collect weather data and measure the effect certain weather parameters have 
on gobbling. This study is a collaboration between the Conservation Department and the 
George Clark Chapter of the National Wild Turkey Federation. 



Approach: 

During 2007, 729 volunteers agreed to collect gobbling data to help us quantify daily and 
seasonal trends in gobbling activity throughout Missouri, and to determine if spring 
season timing is related to peak gobbling. Volunteers participating in gobbling counts 
listened from 15 March through 17 May throughout the state. About 400 participants 
actually collected data throughout the study. We are still attempting to recruit more 
listeners to increase our sample size. The gobble count methodology follows: 



Volunteer listeners (gobbleteers) recruited from throughout state via 
Conservationist magazine, NWTF gobbler publication, Conservation Federation 
of Missouri publications, and in-person recruitment at NWTF turkey banquets. 
Gobble counts were conducted from 15 March through 17 May. 
Gobble count timing was from 45 minutes before sunrise to 30 minutes before 
sunrise 

Gobbleteers listened from a location they chose at least 2 times per week (more 
listening sessions are okay) when winds are lOmph or less and it is not raining. 
The same listening location was used throughout the study. 
Gobbleteers recorded the number of gobbles heard and the number of individual 
gobblers heard during the listening period. 

Gobbleteers recorded nominal weather conditions: temperature, wind speed, 
cloud cover, precipitation during the 12 hours prior to the listening event, etc. 
Key plant species first emergence and/or flowering were be recorded by regional 
coordinators. 

Data were post- stratified to state regions and other meaningful scales for 
analysis. 



Objectives: 

1. Quantify weekly and seasonal trends in gobbling activity in an attempt to define 
peaks of gobbling activity throughout Missouri. 

2. Correlate gobbling activity with a variety of weather related variables to create a 
predictive model for hunters to use. 

3. Correlate gobbling activity with known harvest data to determine if there is a 
relationship between gobbling rates and harvest densities. 



Data analysis: 

While the study will run for 5 years we have conducted some preliminary analysis to look 
for trends associated with the gobbling data. Drawing conclusions from preliminary data 
can be dangerous as trends indicated by the gobbling data may change over time as we 
collect larger sample sizes. At the completion of this 5-year study we will conduct a 
comprehensive analysis and these results will be statistically valid. Results presented 
below were those that suggested a relationship and are the result of simple plots and not 
statistical tests. We also plotted gobbling against a number of weather parameters that 
showed no correlation and these were not included. 

Results: 



Gobbling chronology as related to state regions and 
north/south location 



O 



TO 



> 
< 



Gobbling chronology by state region for 2007 




Central 
Kansas City 
Northeast 
Northwest 
Ozark 
Southeast 
Southwest 
St. Louis 



Listening start date 



Figure 1. Gobbling frequency by Missouri state regions by study week from 
17 March to 15 May, 2007. 



Comments: Most regions of the state showed two peaks of gobbling with 
the first peak near the end of March and the second peak in mid April. 
Northwest Missouri was the exception here and it had only 1 peak in mid 
April. I was surprised to see the consistency among regions for gobbling 
peaks. 



in 

Si 
S3 
O 



Si 

E 

3 
C 

a> 
ns 

1- 

> 
< 



90 



tf> 






Gobbling chronology by North/South location for 2007 




North of Hwy 36 
South of 36, north of 144 
South of 144 



J 






^ 



tf 






^ 



> x 






^ A 



4r r» 






«3° 



Study week start date 



Figure 2. Gobbling frequency by north/south area of Missouri by study week 
from 17 March to 15 May, 2007. 



Comments: These data are similar to the regional gobbling chart except that 
the data from regions were combined into larger categories to give us a 
larger sample size. Areas south of highway 36 showed two peaks of 
gobbling, the first around late March and the second around mid April. The 
area north of highway 36 showed only 1 peak. 



Figure 3. Gobbling frequency by north/south area of Missouri by study week 
from 17 March to 15 May, 2007. 

Comments: This bar graph is representing the same data as show in Figure 2. 



Figure 4. Gobbling frequency by Missouri state regions by study week from 
17 March to 15 May, 2007. 

Comments: This data are similar to Figure 1 except are in bar form and this 
makes it easier to compare regions. The general form of this graph again 
suggests that peak gobbling for most regions occurs during mid April. 



Regional gobbling by week on private lands 



o 

D) 



0) 

n 

E 

3 
C 

<D 
D) 
(0 

&- 

0) 
> 
< 



100 

90 
80 
70 
60 
50 
40 
30 
20 
10 




o^ n<^ 




^ 



^ 



A A 



# 



n^ rf^ 



A<y dr Jr a<F ■ir JF <$? cP 



Central 
Kansas City 
Northeast 
Northwest 
Ozark 
Southeast 
Southwest 
St. Louis 



Study week start date 



Regional gobbling by week on public lands 



o 

S3 
Si 

o 



<u 

Si 

E 



Q) 
O) 
(0 

i— 
0) 

> 

< 



100 
90 
80 
70 
60 
50 
40 
30 
20 
10 





Central 
Kansas City 
Northeast 
Northw est 
Ozark 
Southeast 
Southw est 
St. Louis 



»SJ 



,# 



■& 



^ 



,# 



^ 



■& 



^ v 



<\ 



<y jy ^ ^ ^ ^ N <fi 4> 



& 



o,v rvy 



^ N 



Study week start date 



Figure 5. Gobbling frequency on public and private lands by Missouri state 
regions by study week from 17 March to 15 May, 2007. 



Comments: Gobbling chronology is similar on public and private lands 
however gobbling rates seem higher on private lands and gobbling seems to 
drop off more rapidly on public lands. This may reflect bird densities and/or 
hunting pressure. 



Figure 6. Gobbling frequency on public and private lands by Missouri state 
regions by study week from 17 March to 15 May, 2007. 

Comments: these are the same data depicted in Figure 5 except that they are 
in bar graph form. 



Gobbling rates and frequency as related to weather 
parameters: 



Gobbling frequency as related to cloud cover 



80 



70 

</) 

0> 

S 60 

o 

•S 50 
o 

k. 

CD 

E 40 

E 

3 

C 30 

<L> 
O) 
(0 

5 20 

> 
< 



10 

















■tt 




1^ 


1 








IV 


1 


It 


■ 



A* 



,x* 



„<>" 



^ 



<S> 






is 









_rS> 



is 



n Clear 

■ Partly Cloudy 
□ Mostly Cloudy 
a Overcast 






Figure 7. Gobbling frequency by Missouri state regions by study week 
under various cloud cover conditions from 17 March to 15 May, 2007. 



Comments: There appears to be a clear relationship between gobbling 
frequency and cloud cover. Turkeys were more likely to gobble during days 
with clear skies, followed by days with partly cloudy skies, mostly cloudy 
etc. 



10 



Gobbling frequency and vapor pressure 



300 



250 



S3 
S3 

§) 200 



0> 

I 150 

3 
C 

S, 100 

0) 

< 50 




0.05 0.1 0.15 0.2 0.25 

vapor pressure 



0.3 



0.35 



0.4 



Figure 8. Gobbling frequency by Missouri state regions by study week 
under various vapor pressure from 17 March to 15 May, 2007. 



Comments: Vapor pressure is the pressure exerted by the water vapor 
molecules in a given volume of air. The ratio of vapor pressure to saturation 
vapor pressure multiplied by 100 gives the relative humidity of the air in 
percent. Although not a unconditional relationship it does appear that 
turkeys are more likely to gobble under certain vapor pressures. What was 
not accounted for here was the date and vapor pressure - there may be a 
relationship with gobbling, vapor pressure, and date. This would not be 
apparent with a rough graph. 



11 



Gobbling rates and precipitation during previous 12 hours 



0> 

S3 
S3 
O 



S3 

£ 

3 



4500 
4000 
3500 
3000 
2500 
2000 
1500 
1000 
500 




NO 



YES 



Rain or no rain 



Figure 9. Gobbling frequency as related to precipitation the night before the 
listening period from 17 March to 15 May, 2007. 



Comments: 



Turkeys are more likely to gobble on mornings following a dry night as 
compared to those following rain events. This was one of the strongest 
relationships evident from the study. 



12 



Figure 10. Gobbling frequency by state region as related to precipitation the 
night before the listening period from 17 March to 15 May, 2007. 



Comments: These data are the same as those presented in Figure 9 except 
these are presented by region. The same relationship was evident when 
graphed by region.